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Register a new userTest of lepton flavor violation with Ke2 decay at KLOE
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KLOE Collaboration
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We present a precise measurement of the ratio R_K = Gamma(Ke2(gamma))/Gamma(Kmu2(gamma)) performed with the KLOE detector. The results are based on data collected at the Frascati e^+e^- collider DAFNE for an integrated luminosity of 2.2 fb^{-1}. We find R_K = (2.493pm0.025_{stat}pm0.019_{syst})times 10^{-5}, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation.
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This paper is devoted to the first analyses based on the complete data sample collected by the KLOE detector at DAPHNE, the Frascati phi-factory. The result for the BR(K_S -> gammagamma) and the search for the decay K_S->e+e- are presented. Particular emphasis is put on the measurement of the ratio of Ke2 and Kmu2 BRs.
A preliminary measurement of RK = Gamma(Ke2)/Gamma(Km2) at the KLOE experiment is discussed. The result, RK = (2.55+-0.05+-0.05)x 10^-5, is based on 1.7 fb^-1 of luminosity integrated on the phi-meson peak at the Frascati e^+e^- collider DAFNE, corresponding to ~8000 observed Ke2 events. Perspectives on the methods planned to improve both the statistical and the systematic errors are briefly outlined.
We present measurements of the branching fractions for the decays $Bto K mu^{+}mu^{-}$ and $Bto K e^{+}e^{-}$, and their ratio ($R_{K}$), using a data sample of 711 $fb^{-1}$ that contains $772 times 10^{6}$ $Bbar{B}$ events. The data were collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The ratio $R_{K}$ is measured in five bins of dilepton invariant-mass-squared ($q^{2}$): $q^{2} in (0.1, 4.0), (4.0, 8.12), (1.0, 6.0)$, $(10.2, 12.8)$ and ($>14.18) GeV^{2}/c^{4}$, along with the whole $q^2$ region. The $R_{K}$ value for $q^{2} in (1.0, 6.0) GeV^{2}/c^{4}$ is $1.03^{+0.28}_{-0.24} pm 0.01$. The first and second uncertainties listed are statistical and systematic, respectively. All results for $R_{K}$ are consistent with Standard Model predictions. We also measure $C!P$-averaged isospin asymmetries in the same $q^{2}$ bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the $q^{2}in(1.0,6.0) GeV^{2}/c^{4}$ bin in the mode with muon final states. The measured differential branching fractions, ${dcal B}/{dq^{2}}$, are consistent with theoretical predictions for charged $B$ decays, while the corresponding values are below the expectations for neutral $B$ decays. We have also searched for lepton-flavor-violating $B rightarrow Kmu^{pm}e^{mp}$ decays and set $90%$ confidence-level upper limits on the branching fraction in the range of $10^{-8}$ for $B^{+} rightarrow K^{+}mu^{pm}e^{mp}$, and $B^{0} rightarrow K^{0}mu^{pm}e^{mp}$ modes.
We study lepton flavour violating decays of neutralinos and sleptons within the Minimal Supersymmetric Standard Model, assuming two and three generation mixings in the slepton sector. We take into account the most recent bounds on flavour violating rare lepton decays. Taking the SPS1a scenario as an example, we show that some of the lepton flavour violating branching ratios of neutralinos and sleptons can be sizable (~ 5-10%). We study the impact of the lepton flavour violating neutralino and slepton decays on the di-lepton mass distributions measured at LHC. We find that they can result in novel and characteristic edge structures in the distributions. In particular, double-edge structures can appear in the e tau and mu tau mass spectra if ~tau_1 is the lightest slepton. The appearance of these remarkable structures provides a powerful test of supersymmetric lepton flavour violation at LHC.
We present a comprehensive analysis of the potential sensitivity of the Electron-Ion Collider (EIC) to charged lepton flavor violation (CLFV) in the channel $epto tau X$, within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). We compute the relevant cross sections to leading order in QCD and electroweak corrections and perform simulations of signal and SM background events in various $tau$ decay channels, suggesting simple cuts to enhance the associated estimated efficiencies. To assess the discovery potential of the EIC in $tau$-$e$ transitions, we study the sensitivity of other probes of this physics across a broad range of energy scales, from $pp to e tau X$ at the Large Hadron Collider to decays of $B$ mesons and $tau$ leptons, such as $tau to e gamma$, $tau to e ell^+ ell^-$, and crucially the hadronic modes $tau to e Y$ with $Y in { pi, K, pi pi, K pi, ...}$. We find that electroweak dipole and four-fermion semi-leptonic operators involving light quarks are already strongly constrained by $tau$ decays, while operators involving the $c$ and $b$ quarks present more promising discovery potential for the EIC. An analysis of three models of leptoquarks confirms the expectations based on the SMEFT results. We also identify future directions needed to maximize the reach of the EIC in CLFV searches: these include an optimization of the $tau$ tagger in hadronic channels, an exploration of background suppression through tagging $b$ and $c$ jets in the final state, and a global fit by turning on all SMEFT couplings, which will likely reveal new discovery windows for the EIC.
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